The present invention relates to a lens holding block to be used in light-emitting modules for the optical communication etc.
In the optical communication technology, an electro-optical conversion element such as a laser diode or LED is used as a signal source or light-emitting source. The positioning in an optical system needs to be performed with micron-order accuracy to efficiently introduce light from the above light-emitting element to an optical fiber.
Referring to FIGS. 5 and 6, a description is made of coupling between a lens and a light-emitting element mounted on a chip carrier.
As shown in FIG. 5, a light-emitting element 13 is mounted on a recess 12 of a chip carrier 14, which is provided on the top surface of a block 11. Also provided on the top surface of the block 11 is a metal lens-barrel 16 containing a lens 15 for focusing light emitted from the light-emitting element 13. The positioning between the light-emitting element 13 and the lens 15 is performed such that the lens-barrel 16 is first positioned with respect to the light-emitting element 13 and then fixed using wedge-shaped parts 17. However, the insertion of the wedge-shaped parts 17 may break the once optimized positional relationship between the light-emitting element 13 and the lens 15. Therefore, this type of positioning is deficient in accuracy.
In the case of FIG. 6, instead of using the wedge-shaped parts 17, a lens-barrel 16 containing a lens 15 is pressed against and fixed to the end face of a block 11 on which a chip carrier 14 having a light-emitting element 13 is mounted. While this type of positioning can provide sufficient accuracy within a plane perpendicular to the optical axis, it is also deficient in accuracy in the optical-axis direction because the distance between the lens 15 and the light-emitting element 13 is adjusted visually using a microscope or is dependent on the accuracy of machining.